1. Field of the Invention
The present invention relates to a rear indicating device for an automobile, which device is for indicating various situations including, for example, the application of the brakes of the automobile.
2. Description of Related Art
Recently, a so-called high-mount-type stop-lamp system is often employed on automobiles, wherein a stop-lamp is mounted inside the cabin at a position above a rear shelf in the cabin adjacent to the lower side of the rear window. The high-mount-type stop lamp system is effective in making the stop lamp easily recognized by the driver of a car which is following. However, the high mount type stop lamp system is disadvantageous in that the field of view in the rear direction via the new window is reduced by the stop lamp which is mounted in a location above the rear shelf. Furthermore, due to the use of the high-mount-type stop-lamp system, the space above the rear shelf is reduced and an external appearance of the automobile can be disfigured.
Therefore, in order to avoid the above problems, a system has heretofore been proposed, wherein an automobile rear window is, on its inner surface or its inner side, a hologram, onto which a light, from a light source is illuminated to obtain a reproduction of a red reflected light directed rearwardly via the hologram to indicate the application of the brakes. See, for example, the Japanese Unexamined PCT Patent Publication (Kohyo) No. 1-502465 and Japanese Patent Publication (Kokai) No. 3-121942.
In the indication system as disclosed in the first above mentioned patent (1-502465), optical fibers are connected to an edge of the rear window for the introduction of the light for the reproduction. Such a construction is defective in that a light coupling efficiency between the optical fibers and the edges of the rear window is small. In addition, the small area of the edge of the rear window makes it difficult to introduce a sufficiently large amount of light for the reproduction of the hologram into the pane, which causes the brightness of the indication system to be reduced.
In the indication system as disclosed in the second above mentioned patent (Japanese Patent Publication (Kokai) No. 3-121942), in order to introduce the light row reproduction into the rear window, the light source is directly connected to the edge of the rear or a prism is connected to the edge of the rear for introducing the light, from the light source, into the rear window via the prism. This construction, however, is defective in that a large amount of reproduction light cannot be introduced into the rear window, due to the fact the thickness of the window is as small as about 4 mm, which greatly limits the maximum amount of the light to be introduced.